Rotary or static electromagnetic equipment, such as motors, generators, and transformers, is required to deliver very high efficiency and output density from a viewpoint of energy saving and weight and cost reduction. From a viewpoint of efficiency enhancement, a thinner magnetic thin band or plate making up a core is better and the thickness of magnetic steel sheets in common use is reduced to 0.5 mm to 0.1 mm. The thickness of amorphous alloy thin bands has been reduced to the order of μm.
When the thickness of a plate or a thin band is reduced, eddy current loss, a type of iron loss, can be reduced. Since an eddy current is less prone to pass through a magnetic material high in electrical resistance, between the magnitude of eddy current and the electrical resistance of a core, there is a relation that loss caused by eddy current is low. The electrical resistance of a thin band (or a plate) of magnetic material relates to the length and thickness thereof. The shorter a thin band is, the higher its resistance is. The thinner a thin band is, the higher its resistance is. For this reason, cores formed by laminating plates of a steel sheet are in widest use to obtain low-iron loss cores.
However, it is difficult to apply such a processing method as stamping or lamination to a thin band. The reason for this is as follows: when the thickness of a thin band is reduced, the number of times of processing for making a core having the same dimensions is increased and this increases the cost thereof. Almost all the thin bands are susceptible to external stress; therefore, after machining, such post treatment as annealing is required. In addition, it is very difficult to easily manufacture them.
To manufacture a wound core from a thin band of amorphous alloy, the technology in Patent Document 1 (JP-A-2008-136348) uses a core formed by winding a continuous amorphous ribbon.
Patent Document 2 (JP-A-2009-284578) discloses that the following are effective to reduce eddy current loss: “an insulator is interposed between ribbon-like amorphous alloy and the same,” “a stator core is provided with slits,” and “wound ribbon-like amorphous alloy is cut in the radial direction.”
Patent Document 3 (JP-A-2000-173831) describes an amorphous core for transformers. The following is the contents of the description: “A predetermined number of thin bands of amorphous magnetic alloy are laminated and the obtained laminates are sequentially cut to required lengths. The thus formed multiple unit core element plates different in length are laminated stepwise in a required number of layers to form a core element group equivalent to one block. These core element groups are butt joined together on a block-by-block basis. At this time, over step lap joining in which the butt joints between core element groups are sequentially shifted and step lap joining are combined. A one turn cut-type wound core is thereby formed.”
As mentioned above, many technologies are known with respect to the manufacture of a wound core from a thin band of amorphous alloy.
There are two types of the iron loss of cores, eddy current loss and hysteresis loss. The hysteresis loss can be reduced by annealing. Meanwhile, the eddy current loss relates to such factors as a route through which an eddy current flows and magnetic field strength and the eddy current loss becomes larger with increase in the length of an amorphous ribbon.
For this reason, the amorphous core formed by winding an amorphous ribbon described in Patent Document 1 is easy to be manufactured but it poses a problem of increased eddy current loss. Especially, when it is applied to a high-speed rotary machine, iron loss is significantly increased.
The method for reducing eddy current loss described in Patent Document 2 adopts slit processing so that an eddy current route in a core formed by winding a continuous amorphous ribbon is cut. Therefore, molding for peeling prevention is required. For this reason, the process for forming the core calls for work of winding an amorphous ribbon, annealing and forming work, resin molding work, and slit processing work.
The technique disclosed in Patent Document 2 involves a large number of manufacturing process steps. There is not an easy method for cutting an amorphous core and this increases the manufacturing cost of the core. After an amorphous core is subjected to molding and slit processing, the interior of the core suffers stress and the hysteresis loss is increased. Further, since a hole for a winding jig is left in the center of the core, the utilization ratio of a space is reduced when it is applied to a motor.
Also in the invention disclosed in Patent Document 3, an amorphous alloy laminate may be cut as in that of Patent Document 2. Since the amorphous alloy is very hard, cutting a bock formed of amorphous alloy accelerates wear in jigs and lengthens the cutting time; as a result, the cost becomes very high.
In consideration of the foregoing, it is an object of the invention to provide a wound core formed of a magnetic thin band that enables iron loss and cost reduction, an electromagnetic component and a manufacturing method therefor, and electromagnetic equipment.